Gasifying burner with inert gas curtain between pilot burner and powder burner

ABSTRACT

A burner is provided for gasifying powdered fuel with a free oxygen-containing oxidant at temperatures up to 1900° C. and pressures up to 10 MPa. The burner includes a powder burner part having an oxidant channel and a powdered fuel channel, and a central pilot burner part. An annular channel for the outflow of an inert medium is arranged at the burner mouth between the pilot burner part and the powder burner part.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German Patent Office application No. 102012216505.3 DE filed Sep. 17, 2012. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a burner for gasifying powdered fuel with a free oxygen-containing oxidant at temperatures up to 1900° C. and pressures up to 10 MPa comprising a powder burner part having an oxidant channel and a powdered fuel channel and also a central pilot burner part.

The invention further relates to a gasifying burner having an integrated pilot burner and ignition appliance for gasifying powdered fuels with a free oxygen-containing oxidant at pressures up to 10 MPa and temperatures above the melting point of the inorganic components of the powdered fuels.

BACKGROUND OF INVENTION

Pulverized coal combination burners are known for the partial oxidation of pulverized fuels having a cylindrical water-cooled housing and internal annular spaces for feeding the pulverized fuel and the oxidant. The gasifying burner forms, together with the reaction space delimitation of the gasifier, the inner contour of the gasification space. There is a high thermal stress of the components in contact with the reaction space interior. The technology is extensively described in “Die Veredelung und Umwandlung von Kohle” [Refining and conversion of coal], published by the Deutschen Wissenschaftlichen Gesellschaft für Erdöl, Erdgas und Kohle e.V., [German Scientific Society for Petroleum, Natural Gas and Coal e.V.], December 2008, chapter “GSP-Vergasung” [GSP gasification]. The gasifying burner contains, in the center, a gas-oxygen burner which acts as ignition and pilot burner and is equipped with an optical flame monitoring and a high-voltage emission appliance. It serves for starting up the gasifying burner.

There are also gasifying burners in which the burner end surfaces facing the hot gasification space are water cooled. The supply of the powdered fuel and the gasifying agent are organized in such a manner that intense mixing and reaction occurs directly at the burner mouth, wherein temperatures far above 2000° C. occur in the flame root. The gasification pressure can be up to 10 MPa. In spite of the indirect cooling with water, the burner end surfaces are subject to an extreme thermal stress which leads to increased wear by corrosion and erosion, and greatly limits the availability of the gasifying burners. The problem is additionally intensified in that the pilot burner in the center of the combination burner is operated at an oxygen index of 0.3 to 0.5 and the gas generated in this process is burnt unhindered with the free oxygen-containing gasifying agent and in the process very high temperatures are generated.

SUMMARY OF INVENTION

The problem of the invention is to develop a burner for gasifying powdered fuel in such a manner that the wear on the burner mouth due to the thermal stress is reduced.

The problem is solved by the features of the independent claim(s).

According to the invention, an inert gas curtain is used in order to delay the mixing of the reaction partners and thus keep the flame remote from the burner mouth.

The position and shape of the gasifying and pilot burner flame is modified in such a manner that the heat input into the burner end surfaces facing the hot gasification space is decreased. This is achieved in that the reaction partners oxidant and fuel are separated by one or more inert gas curtains. As a result, the reaction velocity is reduced, the flame is extended, the flame temperature is decreased and the gasification flame is moved away from the burner end surfaces.

Advantageous developments of the invention are specified in the subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail hereinafter as an exemplary embodiment in a scope necessary for understanding, with reference to figures. In the drawings:

FIG. 1 shows a rotationally symmetrical section of a combination burner consisting of pilot burner and powder burner parts having an inert gas curtain between the pilot burner and the oxidant channel of the powder burner part,

FIG. 2 shows a rotationally symmetrical section of a combination burner consisting of pilot burner and powder burner parts having inert gas curtains between the pilot burner and the oxidant channel of the powder burner part and also between the oxidant channel and powder channel of the powder burner part.

DETAILED DESCRIPTION OF INVENTION

In the figures, the same references denote the same elements.

In a gasifying reactor having a gross output of 500 MW, a combination burner according to FIG. 1 is used which consists of a powder burner part 1 and a pilot burner part 2. The combination burner is situated at the top of the gasifying reactor and closes the gasification space at the top. Through the powder channel 3, 72 Mg/h of powdered fuel and through the oxidant channel 4 34 000 Nm³/h of oxygen are fed to the gasification space 5 and are reacted at a pressure of 4.2 MPa and gasification temperatures of 1750° C. to 123 500 Nm³/h of crude synthesis gas, wherein the temperature in this case can rise to 1900° C. The powdered fuel is fed in dense-phase flow with carbon dioxide as transporting gas at a transporting density of 380 kg/m³. In the center of the combination burner, there is situated the pilot burner part 2, to which fuel gas is fed via the fuel gas channel 6 and oxygen is fed via the oxygen channel 7. The pilot burner part 2 is lit and operated in order to set the gasification reactor at the required operating pressure, to ignite the powdered fuel and thereby take up the gasifying operation. The individual channels of the powder burner and pilot burner parts for the powdered fuel and oxidant feed are separated by the cooling channels 8, 9 and 10, through which cooling water flows. In this case, the cooling water pressures and temperatures are selected in such a manner that a boiling state does not occur. Despite the intense cooling, the cooling channels 8, 9 and 10 are exposed to very high temperatures which likewise lead to high temperature gradients between the inner and outer surface of the cooling channels and thus to rapid wear. By applying an inert gas curtain 11, the direct reaction between the gas generated by the pilot burner and the oxygen from the oxidant channel 4 can be prevented or at least delayed. This leads to a lowering of the temperatures and to detachment of the flame from the burner end surfaces. As inert gas, nitrogen, carbon dioxide, steam and mixtures thereof or water can be used.

In a gasifying reactor, under the same conditions as in the present example, a combination burner according to FIG. 2 is used. In addition to the inert gas curtain 11 between the pilot burner part 2 and the oxidant channel 4, an additional inert gas curtain 12 is used between the powdered fuel channel 3 and the oxidant channel 4 of the powder burner part 1, in order to lower the flame temperature further and to lift the gasification flame from the burner end surface. The same inert media can be used as in the previous example. It is also possible to form the inert gas curtain from different inert media.

The invention is also provided by a burner for gasifying powdered fuel with a free oxygen-containing oxidant at temperatures up to 1900° C. and pressures up to 10 MPa, in which, between the annular channel for the oxidant (4) and the outflow for the powdered fuel (3), an annular channel for the outflow of an inert medium (12) is arranged. In a particular development, this burner can be designed by a centrally arranged pilot burner (2) to form a combination burner.

LIST OF REFERENCE SIGNS

-   1 Powder burner part -   2 Pilot burner part -   3 Powdered fuel channel -   4 Oxidant channel -   5 Gasification space -   6 Fuel gas channel -   7 Oxygen channel -   8 Cooling channels -   9 Cooling channels -   10 Cooling channels -   11 Inert gas curtain between the pilot burner part 2 and the oxidant     channel 4 -   12 Inert gas curtain between the oxidant channel 4 and the powdered     fuel channel 3 

1. A burner for gasifying powdered fuel with a free oxygen-containing oxidant at temperatures up to 1900° C. and pressures up to 10 MPa, the burner comprising: a powder burner part having an oxidant channel and a powdered fuel channel, and a central pilot burner part, wherein an annular channel for the outflow of an inert medium is arranged at the burner mouth between the pilot burner part and the powder burner part.
 2. The burner as claimed in claim 1, wherein the oxidant channel of the powder burner part is arranged immediately adjacent to the annular channel for the outflow of the inert medium.
 3. The burner as claimed in claim 1, wherein an annular channel for the outflow of an inert medium is arranged between the oxidant channel and the powdered fuel channel.
 4. The burner as claimed in claim 1, wherein the inert medium is provided by nitrogen.
 5. The burner as claimed in claim 1, wherein the inert medium is provided by carbon dioxide.
 6. The burner as claimed in claim 1, wherein the inert medium is provided by steam.
 7. The burner as claimed in claim 1, wherein the inert medium is provided by water.
 8. The burner as claimed in claim 1, wherein the inert medium is provided by any desired mixture of the group nitrogen, carbon dioxide, steam and water.
 9. The burner as claimed in claim 3, wherein various inert media are provided from the group consisting of nitrogen, carbon dioxide, steam and water for the annular channel for the outflow of an inert medium between pilot burner and powder burner part and also the annular channel for the outflow of an inert medium between the oxidant channel and the powdered fuel channel of the powder burner part. 